[Greg McKaskle]

As Alan said, the IR filter is a physical coating or lens element on the interior portion of the M206 lens.

I learned this when I replaced the lens to change focal length. My color saturation was horrible after that. The new lens was for a monochrome sensor and had no filter.

The camera sensors, a CMOS sensor in this case, is sensitive to the visible spectrum and down into IR. If you do not block IR, the IR light will wash out the image and you will lose color saturation. So camera manufacturers add this to capture the portion of light you typically care about in photography. Alternately, you could block visible light and allow IR through and make it an IR camera. If you have both filters in place, you've made a camera that senses very little.

Greg McKaskle